1. Field of the Invention
This invention pertains to antibodies and fragments thereof, preferably high affinity or avidity antibodies having binding specificity to Hepatocyte Growth Factor (hereinafter “HGF”). The invention also pertains to methods of screening for diseases and disorders associated with HGF, and methods of preventing or treating diseases and disorders associated with HGF by administering said antibodies or fragments thereof.
2. Description of Related Art
Hepatocyte Growth Factor (HGF) (also known as scatter factor (SF) is produced as a single-chain inactive precursor that is cleaved by serine proteases into two chains that are linked by a disulfide bond. (Abounader, R., et al., Neuro-Oncology, 7:436-451 (2005)) The gene encoding HGF is located on chromosome 7q21.1. The biologically active form of HGF is a heterodimer composed of a 69-kDa α-chain and a 34-kDa β-chain. The α-chain contains an N-terminal hairpin domain and 4 kringle domains, while the β-chain contains a serine protease-like domain having no enzymatic activity. Id.
Human Hepatocyte Growth Factor (HGF) is a multifunctional heterodimeric polypeptide produced by mesenchymal cells. HGF has been shown to stimulate angiogenesis, morphogenesis and motogenesis, as well as the growth and scattering of various cell types (Bussolino et al., J. Cell. Biol. 119: 629, 1992; Zarnegar and Michalopoulos, J. Cell. Biol. 129:1177, 1995; Matsumoto et al, Ciba. Found. Symp. 212:198, 1997; Birchmeier and Gherardi, Trends Cell. Biol. 8:404, 1998; Xin et al., Am. J. pathol. 158:1111, 2001). The pleiotropic activities of HGF are mediated through its receptor, a transmembrane tyrosine kinase encoded by the proto-oncogene c-met. In addition to regulating a variety of normal cellular functions, HGF and its receptor c-met have been shown to be involved in the initiation, invasion and metastasis of tumors (Jeffers et al., J. Mol. Med. 74:505, 1996; Comoglio and Trusolino, J. Clin. Invest. 109:857, 2002). HGF/c-met are coexpressed, often over-expressed, on various human solid tumors including tumors derived from lung, colon, rectum, stomach, kidney, ovary, skin, multiple myeloma and thyroid tissue (Prat et al., Int. J. Cancer 49:323, 1991; Chan et al., Oncogene 2:593, 1988; Weidner et al., Am. J. Respir. Cell Mol. Biol, 8:229, 1993; Derksen et al., Blood 99:1405, 2002). HGF acts as an autocrine (Rong et al., Proc. Natl. Acad. Sci. USA 91:4731, 1994; Koochekpour et al., Cancer Res. 57:5391, 1997) and paracrine growth factor (Weidner et al., Am. J. Respir. Cell Mol. Biol. 8:229, 1993) and anti-apoptotic regulator (Gao et al., J. Biol. Chem. 276:47257, 2001) for these tumors.
HGF is a 102 kDa protein with sequence and structural similarity to plasminogen and other enzymes of blood coagulation (Nakamura et al., Nature 342:440, 1989; Weidner et al., Am. J. Respir. Cell. Mol. Biol. 8:229, 1993, each of which is incorporated herein by reference). Human HGF is synthesized as a 728 amino acid precursor (preproHGF), which undergoes intracellular cleavage to an inactive, single chain form (proHGF) (Nakamura et al., Nature 342:440, 1989: Rosen et al., J. Cell. Biol. 127:1783, 1994). Upon extracellular secretion, proHGF is cleaved to yield the biologically active disulfide-linked heterodimeric molecule composed of an alpha-subunit and beta-subunit. (Nakamura et al., Nature 342:440, 1989; Naldini et al., EMBO J. 11:4825, 1992) The alpha-subunit contains 440 residues (69 kDa with glycosylation), consisting of the N-terminal hairpin domain and four kringle domains. The beta-subunit contains 234 residues (34 kDa) and has a serine protease-like domain, which lacks proteolytic activity. Cleavage of HGF is required for receptor activation, but not for receptor binding (Hartmann et al., Proc. Natl. Acad. Sci. USA 89:11574, 1992; Lokker et al., J. Biol. Chem. 288:17145, 1992). HGF contains 4 putative N-glycosylation sites, 1 in the alpha-subunit and 3 in the beta-subunit. HGF has 2 unique cell specific binding sites: a high affinity (Kd=2×10−10 M) binding site for the c-met receptor and a low affinity (Kd=10−9 M) binding site for heparin sulfate proteoglycans (HSPG), which are present on the cell surface and extracellular matrix (Naldinl et al., Oncogene 6:501, 1991; Bardelii et al., J. Biotechnol. 37:109, 1994; Sakata et al., J. Biol. Chem., 272:9457, 1997).
c-met is a member of the class IV protein tyrosine kinase receptor family. The full length c-met gene was cloned and identified as the c-met proto-oncogene (Cooper et al., Nature 311:29, 1984; Park et al., Proc. Natl. Acad. Sci. USA 84:6379, 1987). The c-met receptor is initially synthesized as a single chain, partially glycosylated precursor, p170(MET) (Park et al., Proc. Natl. Acad. Sci. USA 84:6379, 1987; Giordano et al., Nature 339:155, 1989; Giordano et al., Oncogene 4:1383, 1989; Bardelli et al., J. Biotechnol. 37:109, 1994). Upon further glycosylation, the protein is proteolytically cleaved into a heterodimeric 190 kDa mature protein (1385 amino acids), consisting of the 50 kDa alpha-subunit (residues 1-307) and the 145 kDa beta-subunit. The cytoplasmic tyrosine kinase domain of the beta-subunit is involved in signal transduction.
Several different approaches have been investigated to obtain HGF inhibitors or HGF antagonists. Such inhibitors include truncated HGF proteins such as NK1 (N terminal domain plus kringle domain 1: Lokker et al., J. Biol. Chem. 268:17145, 1993); NK2 (N terminal domain plus kringle domains 1 and 2: Chan et al., Science 254:1382, 1991); and NK4 (N-terminal domain plus four kringle domains), which was shown to partially inhibit the primary growth and metastasis of murine lung tumor LLC in a nude mouse model (Kuba et al., Cancer Res. 60:6737, 2000).
As another approach, Dodge (Master's Thesis, San Francisco State University, 1998) generated antagonist anti-c-met monoclonal antibodies (mAbs). One mAb, 5D5, exhibited strong antagonistic activity in ELISA, but induced a proliferative response of c-met-expressing BAF-3 cells, presumably due to dimerization of the membrane receptors. For this reason, a single domain form of the anti-c-met mAb 5D5 has been developed as an antagonist (Nguyen et al., Cancer Gene Ther, 10:840, 2003).
Cao et al., Proc. Natl. Acad. Sci. USA 98:7443, 2001, reported that the administration of a cocktail of three anti-HGF mAbs, which were selected based upon their ability to inhibit the scattering activity of HGF in vitro, were able to inhibit the growth of human tumors in the xenograft nude mouse model.
More recently, neutralizing (inhibitory) anti-HGF mAbs have been reported including L2G7 (Kim et al., Clin Cancer Res 12:1292, 2006, WO 2005/107800, and U.S. Pat. No. 7,220,410 HuL2G7 (WO 2007/115049, the human mAbs described in WO 2005/17107, and the HGF binding proteins described in WO 2007/143090 or WO 2007/143098. It has also been reported that the anti-HGF mAb L2G7, when administered systemically, can strongly inhibit growth or even induce regression of orthotopic (intracranial) glioma xenografts and prolong animal survival (Kim et al., op. cit and WO 2006/130773).
As disclosed herein, HGF promotes the growth and/or scattering of various cell types, and has been shown to be involved in the promotion of angiogenesis, the inhibition of cell growth, and the conversion from a mesenchymal to an epithelial phenotype. Also, both HGF and c-met are expressed in a wide variety of human tumors, and their expression levels is sometimes correlated with poor prognosis. Moreover HGF is believed to play a role in the development of a multitude of diseases and disorders, including but not limited to the development and metastasis of numerous cancers, and the development of macular degeneration. Due to the perceived involvement of HGF in a wide range of diseases and disorders, there remains a need in the art for HGF antagonists and compositions containing and methods useful for preventing or treating diseases associated with HGF, as well as methods of screening to identify patients having diseases or disorders associated with HGF. Particularly preferred are anti-HGF antagonists and compositions containing which effectively inhibit at least one HGF associated biological activity and which elicit minimal or no adverse reactions when administered to a patient. The present invention achieves this objective.